It will depend on how much preprocessing and augmentation is needed. I don't think text needs much preprocessing or augmentation, but for example image classification or detection training needs to create a different augmented image on each iteration and will benefit from a more powerful processor.

Note that you can also use cloud services. If you aren't dealing with confidential data vast ai often is one of the cheapest, otherwise you can use Lambda Labs, Google Engine, AWS or other services. At least in the case of Google Engine and AWS you have to request access to GPU instances, which may take some time.